[AWS] Add Govcloud ARN support

[metrocavich]

Many of the ARN need to be modified not only to allow for different role/bucket/resource names but the second identifier in an ARN
"arn:aws:iam::414351767826:user/databricks-datasets-readonly-user" needs to become something like "arn:aws-us-gov:iam::414351767826:user/databricks-datasets-readonly-user"

We also need to include the appropriate UC roles for Govcloud.

[jdbraun-db]

New top-level folder for AWS gov cloud will be added